Glacier movement is similar to a giant bulldozer scraping a pushing rock and soil but the ice and snow also have plastic properties allowing flow downhill driven by ____________ . If the average separation distance of the pipe is 300 meters, and the elapsed time is 1,500 days, what is the average velocity of the glacier?

a. Gravity
b. Sediment
c. 0.2 meters per day
d. 2 millimeters per day
e. 2 meters per year
f. 2 kilometers per day
g. heat
h. Convection